Water soluble polyvinyl alcohol softened with beta-hydroxy-alkyl ammounium salt



Patented Jan. 27, 1942 UNITED STATES PATENT. or

FICE

WATER SOLUBLE POLYVINYL ALCOHOL .SOFTENED WITH BETA-HYDROXY-ALKYLAIWIVIONIUM SALT William w. Watkins Buflalo, N. Y., assignor to E. I. duPont de Nemours & Company, Wilmington, Del., a corporation of DelawareNo Drawing.

12 Claims.-

signed to place polyvinyl alcohol (which per se is not suitable for sucha use) in the sheet wrapping material and related fields.

It is therefore an object of this invention to prepare modifiedpolyvinyl alcohol compositions. It is a further object to discoversofteners, particularly softeners which are "not too volatile, forpolyvinyl alcohol. It is a still further'object to produce films,threads and the like,.of polyvinyl alcohol which are very much tougherthan polyvinyl alcohol films, threads or the like, hitherto known. Stillanother object is to produce a polyvinyl alcohol film which is not oftoo low softness, especially at low humidities. A general advance in theart, and other objects which will appear hereinafter, are alsocontemplated. 7

These objects are accomplished in general by means of a compositioncomprising polyvinyl alcohol and a water soluble nitrogen-containingalcoholnitrogen salt of the general formula:

. If, (HO-h-lIl-HLZ Rain which R1 is a di-valent aliphatic hydrocarbonradical (residue, nucleus,. group) containing not more than 4 carbonatoms (such as CHzCI-I2--); R2 and R3 are hydrogen or allphatichydrocarbon radicals, the sum of whose carbon atomsdoes not exceed 6; Zis an acid residue such as --OCOCH:, -0COC; I:CH:- COO-, --Cl, :804,=COa, EPO4 or the like, and

a: is the valence ,of the acidresidue whether it be an organic estergroup or an inorganic salt anion.

From the following description,-in which are disclosed certainembodiments of the invention as well-as details as to what is believedto be the best mode'for carrying out .the invention, it will be apparenthow the foregoing" objects and related ends are accomplished. Thequantities are given in parts by weightthroughout the application unlessotherwise specified.

Example I Application January 18, 1941, Serial No. 375,024

ough mixing, this composition was perfectly clear. when cast on to ametal plate it dried to a clear, soft, transparent film, whichmaintained its softness even at low humidities.

, Example II To 100 parts of aqueous 13% polyvinyl alcohol solutionthere was added 4.9 parts of beta-hydroxy-ethylammonium lactate. Themixture was stirred until a clear, homogeneous solution resulted. Filmscast from this solution were found to be clear and transparent, andevidenced 'a high degree of softness at low humidities.

Eaaniple 111 To 100 grams of 13% polyvinyl alcohol solution are added2.3 grams of beta -hydroxy-ethylammonium chloride (sometimes-calledethanolamine hydrochloride"). The mi'xtureis stirred until a clear,homogeneous solution results. Films cast from this solution. are clearand soft, even at low' humidities.

Example IV To 350 grams of 15% polyvinyl alcohol solution, 10.5 gramsofbeta-hydroxy-ethylammonium acetate (frequently called ethanolamineacetate) were added. The solution was stirred until homogeneous, and wasthen cast into-thin films on a metal plate. The films were conditionedfor 48 hours at 85 F. (29.44 C.) and 7% relative humidity.

hol dissolved in water, was added 11%'-(based on the polyvinyl alcoholpresent) beta-hydrox-y droxy-ethylammonium' sulfamate. Afterthorethylammonium formate. The film was cast from this solution-on to anickel surface, and dried thereon. .The resulting film was clear, soft,transparent and maintained its softness even at low humidities.

7 Example VI- 'A fllm was prepared from' a dope consisting of 19%polyvinyl. alcohol (hydroxyl %.,acetyl 5%) and 81% water. Into this dopethere was uniformly incorporated 38% (based on the polyvinyl alcoholpresent) beta-hydroxy-ethylammonium adipate and 2.5% (based on thepolyvinyl alcohol plus softener content ofthe dope) sodium oleate. vTheresulting material was cast on a stainless steel casting wheel and allbut 5% of the water evaporated. The films, which.

stripped easily from the casting whezl, were found to be clear,transparent and possessed a high degree of softness which they retainedeven at low humidities.

' Example VII A dope was prepared consisting of 15.8% of polyvinylalcohol (hydroxyl approximately'l00'%) and 84.2% ofwater. To this dopethere was added 18% (based on the polyvinyl alcohol present)beta-hydroxy-ethylammonium acetate. A thin layer of the resulting dope,after it had been homogenized and freed from bubbles, was cast on to anickel casting belt and the water evapo-' rated. A glass-clear,transparent film 0.001 inch thick, especially suitable for the purposesset out in U. S. A. patent application Serial No. 122,422 of January 26,1937, resulted. I

Example VIII Six hundred (600) parts of potassium hydroxide wasdissolvedin 500 parts'of ethyl alcohol in a vessel equipped with astirrer. solution was added, with thorough agitation, 800 parts ofground polymerized vinyl acetate prepared by polymerizing vinyl acetatewith the aid of benzoyl peroxide. After agitating for about one-halfhour, the polyvinyl acetate saponified and polyvinyl alcoholprecipitated. The'precipitate was separated on a filter, washed withethyl alcohol and dried. v'I'wo thousand (2,000) parts of polyvinylalcohol, prepared in this manner, and 13 parts of ammonium palmitate,were added to a composition .consisting of 8,000 parts of water and 260parts of beta-hydroxy-ethylammonium lactate. The mixture was heatedto atemperature of 90-97 C., and while at that temperature it was thoroughlyagitated for a period of 3 hours. The solution was filtered anddelivered by means of a metering pump to a casting hopper maintained ata suitable temperature.

The solution was converted into a film by flow- To this ing the dope onto the, polished nickel surface I of a rotating casting wheel 6 'feet indiameter, maintained at 85-90 C. As the casting wheel revolved, thelayer of dope was smoothed to a uniform thickness by a doctor knife.With the continued turning of the wheel, the smooth uniform layer ofcasting composition emerged (passed) from the casting chamber into adrying chamber (which enclosed a portion of the casting wheel). Airpassing through the drying chamber at a temperature of approximately 200C. removed the solvent from the composition, so

that after approximately four-fifths of a revolu- I tion of the wheel afllm, which was fairly well set, was secured. The resulting filmstripped without difiiculty from the casting surface, and

was wound into a mill roll for further processing. The film thusprepared was clear, transparent and soft, and retained its softness evenat low humidities.

' Example IX A dope consisting of: A

I Per cent Polyvinyl alcohol (Ex. VI type) -10 Polyvinyl alcohol (Ex.VII type) 5 Water a 85 was prepared, and to the same there was added 7%(based on the polyvinyl alcohol present) beta-hydroxyr-ethylammoniumchloride. The resulting mixture, after homogenization, was castcontinuously on the polished surface of a rotating nickel cylinder 6feet-in diameter. The water was evaporated. and the resulting filmstripped .from the surface of the casting wheel. The film,

which had a thickness of 0.0.0088 inch', was very clear, could besatisfactorily sewed, and had excellent tear resistance.

Example 12' j A film was prepared from a dope consisting of 10%polyvinyl alcohol (hydroxyl 80%, acetyl 20%) and 90% water. Into thisdope there was uniformly incorporated 25% (based on the polyvinylalcohol present) beta-hydroxy-ethylammonium succinate. The resultingmaterial was cast on to a stainless steel casting belt, and the water,evaporated. -A glass-clear, transparent film 0.0009 inch thick, whichpossessed a high degree of softness even at low humidities, resulted.

Example XI A film was prepared from a dope consisting of 30% polyvinylalcohol (-hydroxyl 90%, acetyl 10%) and water. Into this dope there wasuniformly incorporated 5% (based on the polyvinylalcohol present)beta-hydroxy-ethylam-' monium citrate. The resulting material was caston to a stainless steel casting belt, and the-water evaporated. A glass-clear, transparent film 0.0009 inch thick, which possessed a highdegree of softness even at low humidities, resulted.

The preferred beta-hydroxy-ethylammonium salts derived frommono-ethanolamine are betahydroxy-ethylammonium formate,beta-hydrcxyethylammonium acetate, beta-hydroxy-ethylammoniumpropionate. beta-hydroxyethylammonium butyrate,beta-hydroxy-ethylammonium isobutyrate, beta-hydroxy-ethyiammoniumoxalate, beta-hydroxy-ethylammonium malonate,

, hydroxy-propylammonium propionate, and the (including 2:3-butylene,1:2-

butanol-amine butylene and isobutylene links, preferably with thehydroxyl in the beta position) derivatives,

may also be used satisfactorily. The chlorides, phosphates, sulfates andcarbonates are the preferred alkylol amine salts when the acid radicalis inorganic.

vinyl alcohol. This requirement is met by the compounds enumeratedabove, which arecovered by the general formula (HOalky1eneNH:)zZwherein, Z represents the acid radical which should not contain morethan 6 carbon atoms;

and a: is a number equal to the valence of the acid radical. When Zcontains carboxyl groups separated by carbon atoms, the carbon atoms maybe substituted with hydrogen or hydroxyl radicals.

The polyvinyl alcohol may be produced by'the methods known .to the art,for example, by saponifying polymeric vinyl acetate with a 1% solutionof hydrochloric acid in ethanol. At least of the acetate radicals mustbe converted to hydroxyl groups to give satisfactory water solu- 1bility. If more acetate radicals are removed,

other groups may be substituted provided willcient hydroxyl groups togivewater solubility are present. A practically completely saponifiedproduct can be reacted with an aldehyde (formaldehyde, acetaldehyde,propionaldehyde, butyr The compounds (softeners) used, of course, shouldbe compatible with the polyaldehyde, etc.) to produce an acetal of up to8% substitution without loss of water solubility.

The vinyl acetate polymer may be prepared,

for example. by polymerizing monomeric vinyl acetate by means of 0.5%sodium perborate and acetic anhydride.

The polyvinyl alcohol utilizedaccordingjo this invention may be of anydesired viscosity, for- I or after forming into a shaped article. In'cases where the polyvinyl alcohol is coagulated by the dry orevaporative method, the softener is preferably incorporated prior toforming into a shaped article, while when coagulated by contacting witha liquid coagulating bath, the softener is preferably incorporated afterformation into a shaped article.

The amount of softener included in the com position can vary withinquite wide. limits, provided there is sufficient to produce a softeningeffect and not so much that the product formed therefrom becomes sticky.Concentrations of between 5% and (based on the amount of polyvinylalcohol present) have been found most suitable. Because the compoundsvary in their softening effect, the most suitable concentration varies,in a minor manner, in the case of each softener used. 1

Dopes or polyvinyl alcohol evaporative solutions'may contain stripagents to facilitate stripping from the casting wheels orbelts,-espeeially when the stripping takes place while there is still asmall amount of solvent, for example, up to or within the range 5% to15% present. Usually 0.5% to 5% (based on the weight of the polyvinylalcohol plus softener and any other so-called solids which may bepresent) of the strip agent is satisfactory. I

The invention is not limited to the polyvinyl alcohols of the specificexamples, although it peculiarly appertains thereto. Products having amolecular weight in the range 15,000 to 19,000

appear to make the best sheet wrapping and protective covering material.v

Polyvinyl alcohol compositions in accordance withthis invention may bemade up into films,

cles. They aremost useful in the formation of transparent films suitablefor wrapping tissue.

They have particular utility as protective coverings during thehandling, shipping and sewing of articles such as shoes, handbags, andthe like. The leather (natural or imitation), fabric, cloth and relatedmaterials being fabricated are protectedv from marking (by dirt),spotting (by grease), scuffing (by improper handling) etc., by

the covering of polyvinyl alcohol which. is so tough that it can besewed with 10, 20, or even stitches per inch and still have suflicienttear resistance to remain in place during fabrication operations.

Films containing appropriate amounts of these softeners are perfectlyclear and transparent, and are, under given conditions of temperatureand humidity, substantially softer and more durable than films ofunmodified polye vinyl alcohol or those softened with glycerol orglycol. For example, a him made according to Example IV, conditioned at85 F. and 7% relative humidity, made up into a standard rice filled bagand tested in a standard durability tumbling test, averaged 529 dropsper break. A bag made up as Example IV, but softened with a similaramount of glycerin, then conditioned and tested in exactly the samefashion as above, averaged 14 drops per break. The elongation isordinarily at least twice as great as similar films softened-withglycerin.

In the aforementioned durability test, a sample of the film tobetest'ed'is formed into a bag,

and 200 grams of rice inserted therein. The ba is closed so as to leave.the film tightly wrapping the rice, without loose flaps, and sealed bymeans of a piece of pressure-sensitive regenerated-cellulose adhesivetape. The bag is then repeatedly dropped from a height of two feet ontoa glass plate, in an atmosphere of 35% relative humidity. The number oftimes that itcan be dropped without breaking is a direct measure of itstoughness, and may be considered, 1 for the purpose of thisspecification, as the toughness factor.

This specification contains material 'taken' from one' of my co-pending'applications filed November 17, 1937, now U. S. A. Patent No. 2,250,664,issued July 29, 1941.

As many apparently widely different embodiments of .this invention maybe made without departing 'fromthe spirit and scope thereof, it is to beunderstood. that this invention is not limited to thespecific-embodiments thereof except as defined in the appended claims.

I claim:

1. A composition comprising polyvinyl alcohol andbeta-hydroxy-ethylannnonium chloride.

2. A'composition comprising po yvinyl-alcohol andbeta-hydroxy-ethylammonium acetate.

3. A composition comprising water soluble polyvinyl alcohol andb'eta-hydroxy ethylammonium chloride.

4. A transparent sheet comprising water sol- .uble polyvinyl alcoholsoftened with 5% to 25% beta-hydroxy-ethylammonium chloride.

5. A transparent sheet comprising polyvinyl alcohol andbeta-hydroxy-ethyiammonium chloride.

.6. A transparent sheet comprising polyvinyl alcohol and beta hydroxyethylammonium acetate.

'7. A transparent sheet comprising essentially tubes, bottle caps,threads, or other shaped artivinyl alcohol softened with abeta-hydroxy.-

salt.

WILLIAM W. WATKINS.

